Tension control apparatus



1964 R. LE BARON BOWEN, JR 3,145,945

TENSION CONTROL APPARATUS 2 Sheets-Sheet 1 Filed Feb. 15, 1963 INVENTOR.RICHARD LE BARON BOWEN, JR.

ATTORNEYS United States Patent O 3,145,945 TENSION CONTROL APPARATUSRichard Le Baron Bowen, In, 35 Fessenden Road, Barrington, RJ. FiledFeb. 15, 1363, Ser. No. 258,754 9 Claims. (Cl. 242--75.47)

This invention relates to a brake mechanism for applying tension to anunwinding strip or strand of material, and more particularly to a brakemechanism which will automatically maintain a uniform tension on thematerial.

The primary object of the present invention is to provide a brakemechanism for unwinding rolls of material which will automatically applya uniform tension to the material being pulled from the rolls,irrespective of the change in diameter of the rolls.

Another object of the present invention is to provide a brake mechanismfor unwinding rolls which will automatically maintain uniform tensionwithout the use of feed-back sensing controls touching the materialbeing unwound.

Still another object of the present invention is to provide an automatictension control brake which is mechanically simple, yet rugged andpositive in action.

A further object of the present invention is to provide a brakemechanism for unwind tension control wherein the control element consistof a hydromechanical system consisting of a simple mechanicaldifferential gear train and a fluid pump.

A still further object of the present invention is to provide an unwindbrake mechanism which does not have to i be re-set for the start of eachnew roll.

Another object is to provide a combination unwind/ wind-up controldevice.

Other objects of the present invention will be pointed out in part andwill become apparent in part in the following specification and claims.

Many industries, such as the textile, paper, metal, rubber and plastics,have processes which handle the material in process in the form of rollsof the material. These rolls are fed through various processes and it isusually a prerequisite to maintain tension on the material as it leavesthe roll and is drawn into the process machinery. Often a simplemechanical brake is used. However, as

the roll of material decreases in diameter, its speed increases sincethe process is run at a constant speed. This speeds up the rotation ofthemechanical brake, and since the brake produces constant torque unlessits setting is changed it will produce more horsepower and thus put moretension on the material. In such a case tension increases directly withthe increasing revolutions of the unwinding roll, or inversely with thedecreasing diameter of the roll. Manual control of such a simplemechanical brake requires an operator to constantly reduce the brakesetting in an attempt to keep the tension uniform. Such contorl is crudeunder any conditions. Many devices have been provided in attempts toautomatically control the tension on an unwinding roll of material.These have been mechanical, electrical, and hydraulic. However, most arecomplicated, have poor performances, and costly to maintain, and mostobjectionably many require that they be re-set for the start of a newroll.

The present invention is designed as a simple unwind control brakemechanism which is fully automatic and does not need to be re-set. Itcontrol system consists of a simple mechanical differential gear traincoupled with the most elementary fluid system possible: a pump withcontrol valve.

Referring to the drawings in which similar characters of referenceindicate corresponding parts in the figures:

FIGURE 1 shows an embodiment of the present invention in diagrammaticform;

FIGURE 2 shows a modification of part of FIGURE 1;

FIGURE 3 shows a further modification similar to FIGURE 2; and

FIGURE 4 represents another embodiment of the present invention indiagrammatic form, actually representing a modification of FIGURE 3.

Referring to the drawings in more detail, particularly FIGURE 1, a stripor web of material is withdrawn from storage or parent roll 12 at aconstant linear velocity by means of nip rollers 13 and 14, roller 14being driven at a constant speed by means not shown. Roll 12 is fixed tomandrel 15 which has fixed to it a bevel gear 16 which meshes with bevelgear 17 fixed to shaft 18. Shaft 18 is coupled by means of coupling 20to shaft 21 which has fixed to it bevel gear 22 which meshes with bevelgear 23 fixed to the input shaft of bull pump 24. Bull pump 24 drawsfluid from reservoir 25 through suction line 26 and discharges itthrough return line 27 leading from servo-valve 28.

Driven roller 14 has fixed to a shaft extension 30 a bevel gear 31 whichmeshes with bevel gear 32 fixed to shaft 33 which also has fixed to itsprocket 34. A differential gear train, generally indicated by character35, is composed of main shaft 36, idler shaft 37, idler gears 38, inputgear 40 with input sprocket 41 rotatably mounted on shaft 36, and inputgear 42 with input sprocket 43 rotatably mounted on shaft 36. Idlergears 38 mesh with input gear 40 and output gear 42. Input sprocket 41is driven by sprocket 34 on shaft 33 by means of chain 44. Outputsprocket 43 is connected by means of chain 45 to sprocket 46 fixed toshaft 18. The differential thus comprises three elements, namely, theinput element 40, the input element 42 and the main shaft with itsidlers as an element.

Shaft 36 of differential 35 has fixed to it bevel gear 50 which mesheswith bevel gear 51 fixed to the input shaft of pilot-pump 52 having asuction line 53 connecting with reservoir 25. Pilot pump 52 is providedwith discharge line 54 which has a branch 55 leading to servovalve 28,and a return line branch 56 leading to the reservoir 25 through athrottling valve 57.

Servo-valve 28 consists of housing 60 with bore 62 for slidably holdingshuttle 61. One end of bore 62 is reduced as at 63 to provide a seat forthe tapered plug end of shuttle 61. It is apparent that this particularform of valve is used purely by way of illustration, and that any formof pilot-operated servo-valve can be used.

In operation, nip rollers 13, 14 revolve at a constant speed withdrawingstrip 11 from roll 12. The rotation of roll 12 by the tension in strip11 causes bull pump 24 to rotate through the gearing on shafts 18, 21.Rotation of shaft 33 driven by roller 14 causes input gear 40 ofdifferential 35 to rotate. Shaft 18 through roll 12 drives gear 42through sprockets 46, 43. There is always a difference in speed betweengears 40, 42 regardless of the size of roll 12. This speed differencecauses shaft 36 to rotate, thereby causing pilot pump 52 to operate.Pilot pump 52 pulls fluid in through line 53 and discharges it throughline 54. The throttling valve 57 is the main control on this device, andeffectively controls the tension on unwinding strip 11. Throttling valve57 produces back pressure in line 54 and this pressure is transmitted tothe right side of servo-valve 28 by means of line 55. Bull pump drawsfluid through line 26 and discharges it through passage 63 to returnline 27. Shuttle 61 is urged towards the seat provided by restrictedpassage 63 so that the pressure in bore 62 times the area of bore 62 isbalanced by the pressure in passage 63 times the area of passage 63. Ina valve of the configuration shown, the pressure in passage 63 will haveto be greater than that in line 55 for equilibrium to take place. It isevident that, regardless of the pressure in line 55, the pressure inpassage 63 will be proportional to it, and may be calculated bymultiplying the pressure in line 55 by some factor such as K. Otherservo-valves could be provided such at K is equal to 1 or less than 1,rather than greater than 1 as in the illustrated case of servovalve 28in FIGURE 1.

As roll 12 unwinds its diameter becomes increasingly smaller so that thespeed of mandrel 15 likewise increases, inasmuch as strip 11 iswithdrawn as a constant linear velocity. As roll 12 speeds up, shaft 18and sprocket 46 turn faster, thereby tending to speed up gear 42. Thisslows down shaft 36 thereby slowing down pilot pump 52. Throttling valve57 acts as a fixed restriction in discharge line 56 so that as pilotpump 52 slows down the pressure in line 55 decreases. This reduces thepressure in passage 63 proportionally. If the pressure in passage 63were not changed as roll 12 unwound and bull pump 24 speeded up, thetorque produced by bull pump 24 would increase proportionally to thespeed increase and this would increase the tension in strip 11proportionally. However, with the present invention, as the speed ofbull pump 24 increases the pressure in passage 63 on the discharge ofbull pump 24 decreases so that the torque on the bull pump 24 decreases,thereby tending to maintain the tension on strip 11 at a more or lessuniform value, rather than increasing it constantly. The tension at anypoint in the unwind history of roll 12 may be adjusted by adjustingthrottling valve 57.

FIGURE 2 shows a modification of FIGURE 1, wherein bull pump 24 isreplaced by a mechanical brake generally indicated by referencecharacter 70, with element 71 fixed against rotation and rotatingelement 72 with lining 73 fixed to shaft 21a connected to coupling 20.Shaft 18 and all other operating parts are as shown in FIGURE 1,including pilot pump 52 and pressure line 55. However, in FIGURE 2pressure line 55 leads to servo-valve 28a, a modification of theoriginal servo-valve 28 shown in FIGURE 1. Servo-valve 28a is basicallythe same as servo-valve 28, except that it is designed for handling gas(air) rather than liquids, and therefore has ports 74 for exhausting thefluid to the surroundings. A line 75 connects servo-valve 28a tocylinder 76 fitted with piston 77 fixed to stationary brake element 71.Connected to line 75 is line 78 with valve for introducing fluid to line75 and cylinder 76. The pressure in cylinder 76 is controlled by thethrottling action of servo-valve 28a.

In operation the mechanism shown in FIGURE 2 operates much the same asFIGURE 1. As the roll unwinds pilot pump 52 slows down pumping lessfluid through valve 57 thereby reducing the pressure in line 55 leadingto servo-valve 28a, likewise reducing the throttled fluid pressure inline 75 and cylinder 76. This effectively reduces the torque applied bybrake 70 to roll 12, thereby tending to maintain the tension in strip 11more or less uniform.

FIGURE 3 shows a further modification in which brake 7 has been replacedby a slip clutch 80 so that the mechanism may be used for unwinding aroll and then reversing the process machinery and winding up the roll.Slip clutch 80 has a rotatable element 72 fixed to shaft 21a as inFIGURE 2. Opposing clutch element 81 has fixed to it a sprocket 82 whichis connected by chain 83 to sprocket 84 fixed to shaft 85. Shaft 85 is apower input shaft with a ratchet 86 to permit rotation in only onedirection.

In operation it is necessary to consider two conditions in FIGURE 3, onewhen unwinding a roll and two when winding up a roll from a startingcore. When FIGURE 3 is run as an unwind, its operation is identical toFIG- URE 2, since ratchet 36 prevents shaft 85 and clutch element 81from rotating, so that clutch 80 is for all intents and purposes amechanical friction brake as in FIGURE 2. Piston 77a urges element 81towards element 72 just as piston 77 urges element 71 towards rotatingelement 72 in FIGURE 2. When the mechanism works as a windup drive,rollers 13, 14 in FIGURE 1 rotate so as to feed strip 11 to roll 12.Shafts 33, 18 and differential all rotate in a direction opposite fromwhen the mechanism is used in unwinding. In this instance when thedevice is used as an unwind-windup drive, pilot pump 52 must be of thereversible type wherein rotation in either direaction produces flowthrough line 54 to pressurize line 55. As a windup, pilot pump 52progressively speeds up as the roll 12 increases in diameter, producingincreasing pressure in line so that servo-valve 28a producesprogressively higher pressures in line thereby increasing the torqueapplied by clutch as roll 12 winds up, maintaining the tension in thestrip 11 more or less uniform. Power input shaft could be driven by anelectric motor which would be energized when roll 12 was winding up, butwould not be energized when roll 12 was unwinding. Or power input shaft85 could be driven from roller 14 with a suitable one way clutchinstalled so that no motion would result when rollers 13, 14 werewithdrawing strip 11 from roll 12.

FIGURE 4 shows a modification of FIGURE 3 and as such is a furthermodification of FIGURE 1. In FI URE 4 the slip clutch 31 of FIGURE 3 hasbeen replaced by a differential gear train generally indicated by 108and tension pump 24. Differential 111i is mounted on shaft 101 withcross shafts 192. Fixed to shaft 101 at one end is gear 103 meshing withgear 16 fixed to the mandrel of roll 12. Fixed to roller 14 is gear 31which meshes with gear 104 fixed to shaft 105. Also fixed to shaft 165is one element of overrunning clutch 106 which is additionally providedwith ratchet 108. Sprocket 107 is fixed to the other element ofoverrunning clutch 106 and is connected by means of chain 110 tosprocket 111 fixed to gear 112 rotatably mounted on shaft 101. Gear 112meshes with gears 113 rotatably mounted on shafts 102 and gears 113 meshwith gear 114 rotatably mounted on shaft 101. Sprocket 115 fixed to gear114 connects by means of chain 117 with sprocket 116 fixed to shaft 118which has fixed to it gear 120 which meshes with gear 23 on tension pump24.

A second differential gear train generally indicated by 121 is mountedon shaft 122 with cross shafts 123. Power input to differential 121 isfrom gear 124 fixed to shaft 105 and gear 125 fixed to shaft 122.Differential 121 is connected to shaft 101 by means of sprocket 126which by means of chain 127 drives sprocket 128 fixed to gear 130rotatably mounted on shaft 122. Gear 130 meshes with idler gears 131which mesh with gear 132 rotatably mounted on shaft 122. Gear 132 hasfixed to it a sprocket 133 which by means of chain 134 is connected tosprocket 135 fixed to shaft 136 which has fixed to it gear 137 whichmeshes with gear 51 fixed to the input shaft of pilot pump 52. In thiscase both tension pump 24 and pilot pump 52 are of the reversible typesuch that regardless of the rotation of their input shafts discharge isin the same direction. The fluid system connecting pumps 24, 52 isidentical to that shown in FIGURE 1 in all other respects.

In operation of FIGURE 4 we have two conditions to consider as in FIGURE3. First consider that the mechanism is being used as an unwind controlso that rollers 13, 14 which are powered by a source (not shown) areturning in such a direction so as to withdraw strip material 11 fromroll 12. When turning in this direction ratchet 108 is locked so thatshaft 105 rotates and sprocket 107 remains stationary holding gear 112on differential 109 from rotating. With gear 112 fixed against rotationdifferential gear train 1% simply becomes an idler gear train with afixed ratio. Thus tension pump 24 will be turned in direct proportion tothe speed of shaft 101,

which in turn has a speed proportional to the diameter of roll 12.Therefore, when acting as an unwind mechanism FIGURE 4 is identical toFIGURE 1 since the gear train 100 does not act as a difierential butrather as a simple gear train with one input and one output.

It is when used as a wind-up mechanism that the differential 1% inFIGURE 4 comes into use. In such a case, rollers 13, 14 are driven by asource of power (not shown) and turn in such a direction as to feedstrip 11 to roll 12. In this case overrunning clutch 106 drives sprocket107 and thus input gear 112 of differential 109. When power is put intogear 112 this produces reaction torque on both shaft 161 and shaft 118.Since shaft 101 must turn at a predetermined speed to wind up the roll12, pump 24 is forced to turn at a specific speed. As roll 12 winds upits speed decreases thereby increasing the speed of tension pump 24.Differential 121 acts as described in FIGURE 3 so that as pump 24 speedsup pilot pump 52 also speeds up thereby automatically increasing theback pressure on tension pump 24 and tending to maintain the tension instrip 11 more or less constant.

I claim:

1. In an unwinding apparatus, a roll of material, means for withdrawingsaid material, a brake mechanism for applying a drag on said roll, adriving connection between said roll and said brake mechanism, adifferential gear train comprising three rotatable power transmittingelements, a driving connection between the first of said elements andsaid means for withdrawing said material, a driving connection betweenthe second of said elements and said roll, a fluid pump, a control valvein the discharge of said pump for producing back pressure, a drivingconnection between the third of said elements and said fluid pump, andmeans whereby the pressure produced by said pump controls the amount ofdrag applied by said braking mechanism.

2. In an unwinding apparatus, a roll of material, means for withdrawingsaid material, a brake mechanism for applying drag on said material, adriving connection between said roll and said brake mechanism, adifferential gear train comprising three rotatable power transmittingelements, a driving connection between the first of said elements andsaid means for withdrawing said material, a driving connection betweenthe second of said elements and said roll, a fluid pump, means forthrottling the discharge from said pump to produce a back pressure, adriving connection between the third of said elements and said fluidpump, and means whereby the pressure produced by said pump controls theamount of drag applied by said braking mechanism.

3. An apparatus as in claim 2 wherein said brake mechanism is a secondfluid pump.

4. An apparatus as in claim 2 wherein said brake mechanism is amechanical brake.

5. An apparatus as in claim 2 wherein said brake mechanism is a secondfluid pump and said means for controlling the drag is a servo-valve inthe discharge of said second pump, said servo-valve being actuated bythe pressure on said first pump.

6. In an apparatus for winding or unwinding, a roll of material, meansfor withdrawing said material from said roll or for feeding saidmaterial to said roll, a slipping drive mechanism comprising an inputshaft and an output shaft, said slipping drive connection being capableof producing variable torque, means for driving said input shaft whensaid apparatus is used for winding, means for locking said input shaftwhen said apparatus is used for unwinding, a driving connection betweensaid output shaft and said roll, a diiferential gear train comprisingthree rotatable power transmitting elements, a driving connectionbetween the first of said elements and said means for withdrawing saidmaterial or for feeding said material, a driving connection between thesecond of said elements and said roll, a fluid pump, means forthrottling the discharge from said pump to produce back pressure, adriving connection between the third of said elements and said fluidpump, and means whereby the pressure produced by said pump controls theamount of torque produced by said slipping drive connection.

7. An apparatus as in claim 6 wherein said slipping drive connectionconsists of a slip clutch.

8. An apparatus as in claim 6 wherein said slipping drive connectionconsists of a second differential gear train with a second fluid pumpconnected to one of the three power transmitting elements of said seconddif ferential.

9. An apparatus as in claim 6 wherein said slipping drive connectionconsists of a second differential gear train with a second fluid pumpconnected to one of the three power transmitting elements of said seconddif ferential, and said means for controlling the torque consists of aservo-valve in the discharge of said second pump, said servo-valve beingactuated by the pressure produced by said first pump.

References Cited in the file of this patent UNITED STATES PATENTS2,859,923 Bowen Nov. 11, 1958 2,883,122 Bowen Apr. 21, 1959 2,937,819Bowen May 24, 1960

1. IN AN UNWINDING APPARATUS, A ROLL OF MATERIAL, MEANS FOR WITHDRAWINGSAID MATERIAL, A BRAKE MECHANISM FOR APPLYING A DRAG ON SAID ROLL, ADRIVING CONNECTION BETWEEN SAID ROLL AND SAID BRAKE MECHANISM, ADIFFERENTIAL GEAR TRAIN COMPRISING THREE ROTATABLE POWER TRANSMITTINGELEMENTS, A DRIVING CONNECTION BETWEEN THE FIRST OF SAID ELEMENTS ANDSAID MEANS FOR WITHDRAWING SAID MATERIAL, A DRIVING CONNECTION BETWEENTHE SECOND OF SAID ELEMENTS AND SAID ROLL, A FLUID PUMP, A CONTROL VALVEIN THE DISCHARGE OF SAID PUMP FOR PRODUCING BACK PRESSURE, A DRIVINGCONNECTION BETWEEN THE THIRD OF SAID ELEMENTS AND SAID FLUID PUMP, ANDMEANS WHEREBY THE PRESSURE PRODUCED BY SAID PUMP CONTROLS THE AMOUNT OFDRAG APPLIED BY SAID BRAKING MECHANISM.